TEHRAN: Iran’s nuclear chief said on Friday the country has started making more efficient centrifuge models that it plans to put in use by early 2011 — a statement that underscores Tehran’s defiance and adds to international concerns over its nuclear ambitions.

Ali Akbar Salehi said Iranian scientists are still testing the more advanced models before they will become operational at the country’s enrichment facilities. He said Tehran will start full-scale uranium enrichment production by March 2011.

Tehran has been saying since April that it is building more advanced centrifuges capable of enriching uranium with higher efficiency and precision, but Salehi’s remarks were the first indication of a timeline when the new models could become operational. The new centrifuge models will be able to enrich uranium much faster than the old ones — which would add to growing concerns in the West because they would allow Tehran to accelerate the pace of its program. That would mean Iran could amass more material in a shorter space of time that could be turned into the fissile core of missiles, should Tehran choose to do so.

Iran’s uranium enrichment is a major concern to the international community, worried that the program masks efforts to make a nuclear weapon. Tehran insists its enrichment work is peaceful and only meant to generate electricity, not make an atomic bomb. Iran has threatened to expand its enrichment program tenfold, even while rejecting a plan brokered by the UN agency.